Dynamic tax calculator

[Roofasa]

I'm pretty stuck and confused as hell
Every time I try to do something, i get subscript out of range.
So I think there is a problem here:

arrBreakPoint = Range("a4:a7").Value
arrTaxPct = Range("b4:b7").Value
For i = LBound(arrBreakPoint) To UBound(arrBreakPoint)

Am I setting up my for loop wrong?